A wide variety of bioreactor technologies has been developed for the treatment of solid, liquid, and gaseous matrices contaminated with myriad organic chemicals (Grady, C. P. L., Jr. [1989] In Biotechnology Application in Hazardous Waste Treatment, Lewandowski, G., et al., Eds., Engineering Foundation: New York, pp. 81-93). Bioreactors are, in general, advantageous as compared to other bioremediation approaches (e.g., composting, land farming, and in situ treatment) because the physicochemical variables (e.g., pH, nutrient concentrations, biomass, oxygen-transfer rate, contaminant loading rate, etc.) of a bioreactor can be precisely controlled. Conditions in a bioreactor can be optimized for the desired microbial activities in order to maximize performance. Effective mixing alleviates certain mass-transfer problems, and surfactants, detergents, or solubilizing agents can be added to increase the aqueous solubility of hydrophobic contaminants, thereby enhancing the bioavailability of target chemicals. For these same reasons, bioreactor inoculation is often a viable technique to rapidly establish active biomass and enhance the desired biological activity. Together, these factors act to maximize the kinetics of biodegradation, hence enhancing the bioremediation processes.
Bioreactor strategies have been applied successfully for the bioremediation of organic contaminants. For example, biofiltration has been used extensively to remove volatile organic compounds from air emissions (Kampbell, D. H., J. T. Wilson, H. W. Read, T. T. Stocksdale [1987] J. Air Pollut. Control Assoc. 37:1236-1240; Leson, G., A. M. Winer [1991] J. Air. Waste Manage. Assoc. 41:1045-1054), vapor-phase bioreactors have treated chlorinated aliphatics in the gaseous state (Folsom, B. R., P. J. Chapman [1991] J. Appl. Environ. Microbiol. 57:1602-1608; Friday, D. D., R. J. Portier [1991] Environ. Prog. 10:30-39), and fixed film bioreactors have been used for the treatment of kraft bleaching effluent containing a variety of chlorinated aromatic chemicals (Salkinoja-Salonen, M. S., R. Hakulinen, R. Valo, Apajalahti [1983] J. Water Sci. Technol. 15:309-319) and for petroleum refinery effluent (Hamoda, M. F., A. A. Al-Haddad [1987] J. Inst. Water Environ. Manage. 1:239-246).
Attempts to apply bioreactor technologies to the treatment of soil and water contaminated with the chemicals found in organic wood preservatives have often proven unsuccessful (Dooley-Dana, M., M. Findley [1989] Abstracts, American Society for Microbiology, Annual Meeting, May 14-18, 1989, New Orleans, L. A., p. 363; Mahaffey, W., R. Sanford, A. Strehler, A. Bourquin, Id. at 338; Mueller, J. G., S. E. Lantz, B. O. Blattmann, P. Chapman [1991] J. Environ. Sci. Technol. 25:1055-1061; Mueller, J. G., D. P. Middaugh, S. E. Lantz, P. J. Chapman [1991] J. Appl. Environ. Microbiol. 57:1277-1285; van der Hoek, J. P., L. G. Urlings, C. M. Grobben [1989] Environ. Technol. Lett. 10:185-194; Webb, O. F., T. L. Phelps, P. R. Bienkowski, P. DiGrazia, G. D. Reed, B. Applegate, D. C. White, G. S. Sayler [1991] J. Appl. Biochem. Biotechnol. 28/29:5-19). One challenge which remains in the field of bioremediation is the limited ability to efficiently biodegrade high molecular weight polycyclic (chemicals containing four or more fused rings) aromatic hydrocarbons (HMW PAHs) present in contaminated soils and waters. Creosote is a commonly encountered wood preservative containing HMW PAHs which have previously been difficult to biodegrade. This limited success in degrading HMW PAHs is due to structural aspects of these chemicals and their strong tendency to partition to biomass, sludge, and bioreactor residues (Petrasek, A. C., I. J. Kugelman, B. M. Austern, T. A. Pressly, L. A. Winslow, R. H. Wise [1983] Water Pollut. Control Fed. 55:1286-1296; Jafvert, C. T., J. K. Heath [1991] Environ. Sci. Technol. 25:1031-1038; Jafvert, C. T. [1991] Environ. Sci. Technol. 25:1039-1045).
Previously, we described the isolation and characterization of microorganisms capable of utilizing HMW PAHs and other persistent creosote constituents as sole sources of carbon and energy for growth (Mueller, J. G., P. J. Chapman, P. H. Pritchard [1989] Appl. Environ. Microbbl. 55:3085-3090; Mueller, J. G., P. J. Chapman, B. O. Blattman, P. H. Pritchard [1990] Appl. Environ. Microbiol. 56:1079-1086). See also U.S. Pat. No. 5,132,224. Additionally, an axenic culture of Pseudornonas sp. strain SR3 was shown to mineralize PCP when supplied as a sole carbon source in liquid medium (Resnick, S. M., P. J. Chapman [1990] Abstracts, American Society for Microbiology, Annual Meeting, May 13-17, 1990, Anaheim, Calif., p. 300). A Pseudomonas paucimobilis strain known as EPA-505 has been described as capable of degrading high molecular weight PAHs and PCP. U.S. Pat. No. 5,132,224. However, the viability of these organisms can be inhibited by the PAHs of lower molecular weight and heterocyclic compounds found on creosote, as well as by certain phenolic compounds. Therefore, a need exists for a strategy to remove HMW PAHs and PCP by bioremediation without affecting the viability of the organisms used in the bioremediation process.